The Object Is The Construction Of Momentum Spectrometer For Molecular Processes In Boundary Plasma And The Collision Process Between Low Energy Electrons And Hydrocarbon Molecules

Most of the visible substances in universe are plasmas. The study of plasmas not only provides a tool to explore the vast universe, but also offers a significant support to development in modern technology. The urgent demands for new and clean energy source boost the researches on plasmas, which are very important for controlled fusion. The Tokamak device is one of the most potential approaches to achieve the controlled fusion power. Plasma and wall interaction (PWI) directly determines the security in operations and service life of the device.The electron impact ionization and dissociation of hydrocarbon molecules are one of basic physics processes in PWI of Tokomak, and a large number of complete and detailed experimental data for these processes are in urgent need. The theme of this thesis is to construct the experimental method based on RIMS and study low-energy electron collision of hydrocarbon molecules. Detailed works are listed below:Ⅰ. A cold target recoil-ion momentum spectroscopy (COLTRIMS) is constructed and optimized. Including time-of-flight spectrometer system, detector system and data acquisition systems, and supersonic gas beam injection system are in good condition. The resolution of the position sensitive detector, which is based on the delay line anode and MCP, is better than100μm. From the gas injection system, a supersonic cold gas beam with a diameter of～2mm and a density of1012/cm3can be produced for the collision platform.Ⅱ. A pulsed electron beam injection system has been established by coupling an ultrafast power supply with the gate of electron gun. The system can provide a1ns low-energy pulsed electron beam with a repetition of20kHz and intensity of～100pA. Square coils have been used to generate magnetic field to compensate the earth magnetic field and the remaining stray magnetic fields is less than20mGs. The injection system can provide pulsed electron beam even at ultra-low energy of20eV. So experiments of electron impact ionization and dissociation for almost all kinds of hydrocarbon molecules beacome feasible.Ⅲ. Electron impact ionization dissociation processes of hydrocarbon molecules (CH4, C2H6and C2H4) have been studied based on theoretical calculation and measurement by RIMS. Theoretical dissociation energy of dissociation channel is deduced by calculating energies of stationary systems through "Gaussian" program. In present experiment we measured the kinetic energy of recoil-ion with the resolution of～10meV, which is much better than earlier experiments. Kinetic energy distributions of recoil-ions are shown and their average values are plotted as functions of impact electron energy for each sort of molecular ion. Accurate mean KER (kinetic energy released) value during dissociation is obtained after estimating the contribution from gas target. Due to high resolution and accurate results, present investigation allows detailed analysis of the dissociation reaction channels. We also studied the dissociation of C2H4++which is according to Coulomb explosion and decays into two fragment ions.